1. Field of the Invention
The present invention relates to a method of quantitatively evaluating a front of screen quality of, preferably, an LCD (Liquid Crystal Display) panel which is mainly used as a display for a notebook PC, and an apparatus for evaluating the front of screen quality using the same.
2. Description of the Related Art
Recently, an LCD panel, for example, has been widely used as a display for a notebook PC or the like. This LCD panel may have a defect such as non-uniformity. When the LCD panel has such a defect beyond a limit, the LCD panel cannot be used as the display. Thus, it is necessary to evaluate a front of screen quality of each LCD panel. The evaluation of the front of screen quality has been heretofore performed in the following manner. A quality boundary sample for the non-uniformity or the like is made in accordance with a front of screen quality criterion of liquid crystal display. Then, a measurer visually compares the sample and the LCD panel to be checked, thereby determining whether or not the LCD panel is defective.
The above-described conventional method of evaluating the front of screen quality has the following problems due to the evaluation by the measurer.
1) The comparison between the quality boundary sample and the LCD panel depends on a human sense. Moreover, the non-uniformity of the sample vary in shape or the like. Therefore, the comparison needs a human discretion and thus a measured value is prone to depend on the measurer, or the comparison requires a visual alignment by the measurer.
2) The determination is basically made in accordance with information about a luminance difference and an area. Thus, the non-uniformity due to a steep luminance difference such as a lack of dots or lines are ambiguously discriminated from the non-uniformity due to a gentle gradation. Consequently, the determination may differ depending on the measurers.
The present invention is directed to a method and an apparatus for quantitatively evaluating a front of screen of a screen to be checked. In this method of evaluating the front of screen quality, preferably, an image of an LCD panel is captured and the captured image is processed and evaluated in a state in which the screen to be checked of the LCD panel is on. The apparatus for evaluating the front of screen quality comprises an image capturing apparatus for detecting an absolute value of luminance, and a data processing apparatus for processing captured image data. The apparatus is constituted so as to carry out the above-described method of evaluating the front of screen quality. In the present invention, a manual evaluation is not performed at all. Thus, the front of screen quality of the screen to be checked of the LCD panel or the like, for example, can be quantitatively evaluated.